package com.fulin.sycnLife;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;

public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job>{

	//线程池最大限制数
	private static final int MAX_MORKER_NUMBERS = 10;
	
	//线程池默认的数量
	private static final int DEFAULT_WORKER_NUMBERS = 5;
	
	//线程池最小的数量
	private static final int MIN_WORKER_NUMBERS = 1;
	
	//这是一个任务列表，将会向里面插入工作
	private final LinkedList<Job> jobs = new LinkedList<Job>();
	
	//工作者列表
	private final List<Worker> workers = Collections.synchronizedList(new ArrayList<Worker>());
	
	//工作者线程的数量
	private int workerNum = DEFAULT_WORKER_NUMBERS;
	
	//线程编号生成
	private AtomicLong threadNum = new AtomicLong();
	
	public DefaultThreadPool(){
		initializeWorkers(DEFAULT_WORKER_NUMBERS);
	}
	
	public DefaultThreadPool(int num){
		workerNum = num > MAX_MORKER_NUMBERS ? MAX_MORKER_NUMBERS : num < MIN_WORKER_NUMBERS ? MIN_WORKER_NUMBERS : num;
		initializeWorkers(workerNum);
	}
	
	@Override
	public void execute(Job job) {
		if(job != null){
			//添加一个任务，然后进行通知
			synchronized(jobs){
				jobs.addLast(job);
				jobs.notify();
			}
		}
	}

	@Override
	public void shutdown() {
		for(Worker worker : workers){
			worker.shutdown();
		}
	}

	@Override
	public void addWorkers(int num) {
		synchronized(jobs){
			//限制增加的worker数量不能超过最大值
			if(num + this.workerNum > MAX_MORKER_NUMBERS){
				num = MAX_MORKER_NUMBERS - this.workerNum;
			}
			initializeWorkers(num);
			this.workerNum += num;
		}
	}

	@Override
	public void removeWorker(int num) {
		synchronized(jobs){
			if(num > this.workerNum){
				throw new IllegalArgumentException("beyond workNum");
			}
			int count = 0;
			while(count < num){
				Worker worker = workers.get(count);
				if(workers.remove(worker)){
					count ++;
				}
			}
			this.workerNum -= count;
		}
		
	}

	@Override
	public int getJobSize() {
		return jobs.size();
	}

	//初始化线程工作者
	private void initializeWorkers(int num){
		for(int i = 0;i < num ;i++){
			Worker worker = new Worker();
			workers.add(worker);
			Thread thread = new Thread(worker,"ThreadPool-Worker-" + threadNum.incrementAndGet());
			thread.start();
		}
	}
	
	//工作者,负责消费任务
	class Worker implements Runnable{

		//是否工作
		private volatile boolean running = true;
		
		@Override
		public void run() {
			while(running){
				Job job = null;
				synchronized(jobs){
					//如果工作者列表为空，那么久wait
					while(jobs.isEmpty()){
						try{
							jobs.wait();
						}catch(InterruptedException ex){
							Thread.currentThread().interrupt();
							return;
						}
					}
					job = jobs.removeFirst();
				}
				if(job != null){
					try{
						job.run();
					}catch(Exception ex){
						//忽略任务执行中的Exception
					}
				}
			}
		}
		
		public void shutdown(){
			running = false;
		}
	}
}
